Radiant energy device



NOV. 23, 1965 w, HQDGE 3,219,872

RADIANT ENERGY DEVICE Filed Sept. 19, 1962 Invervtor: WiLLiam "F. Hodge b Mr? 8 His A Lv-b' vne United States Patent 3,219,872 RADIANT ENERGY DEVICE William F. Hodge, Lyndliurst, Ohio, assignor to General Electric Company, a corporation of New York Filed Sept. 19, 1962, Ser. No. 224,736 1 Claim. (Cl. 313316) This invention relates generally to radiant energy devices, and more particularly to infrared lamps of the type comprising an elongated tubular envelope having an incandescible filament of coiled tungsten wire extending therethrough and operable at temperatures of at least about 2400 K.

It is an object of the invention to provide devices of this type having envelopes of small diameter and operating at high intensity over an extended length. It is also an object to provide a coiled filament structure of small coil diameter but high power consumption per unit of length.

There have been available commercially infrared lamps of the general type described above and comprising tubular quartz envelopes of about inch outside diameter and containing a helically coiled tungsten filament consuming as much as 200 watts per inch of coil length at an applied voltage of 24 volts per inch and operating at about 2500 K. color temperature. For certain purposes Where extremely high heat intensity is required, such lamps are frequently used in arrays with a minimum spacing between lamps and at a maximum over-voltage with consequent shortened life. There has been a demand for lamps of appreciably higher Wattage in the same envelope diameter. However, higher wattages require a heavier and larger diameter filament coil which becomes impractical because of its close proximity to the envelope wall which results in softening of the envelope. Similarly, it may become desirable to use envelopes of still smaller diameter with proportionately high output.

It is also advantageous to provide a high wattage filament coil structure of small diameter even in cases where envelope diameter is not a limitation. For example, a slim linear source of minimum diameter is desirable for use in photocopy machines.

In accordance with the invention, the objectives are achieved by an arrangement of two concentric helical coils, one within the other and electrically connected in parallel. The outer coil may be formed of wire consuming a maximum of wattage for a coil diameter of given size, and it is supplemented by an additional smaller diameter coil arranged concentrically within and coextensive with the outer coil.

Further features and advantages of the invention will appear from the following detailed description of a species thereof and from the drawing wherein:

FIG. 1 is a side view of an infrared ray generator comprising the invention; and

FIG. 2 is an enlarged section of a portion of the concentric filament arrangement showing its connection to one of the lead-in conductors.

Referring to FIG. 1 of the drawing, the device shown therein is of the type disclosed and claimed in Patent 2,864,025Foote et al., and comprising a sealed elongated tubular envelope 1 preferably consisting essentially of fused silica or quartz. The envelope contains an inert gas filling, preferably argon, and is closed at its ends by pinch seals 2 through which extend lead-in conductors 3, preferably of molybdenum wire having thin foliated intermediate portions 4 hermetically sealed in the respective pinch seals. An incandescible tungsten filament structure 5 extends axially of the envelope 1 between said lead-in conductors 3 and is supported in the axis of the envelope by a plurality of support members 6 engageable with the inner envelope wall.

As shown in FIG. 2, the filament structure 5 is composed of outer and inner concentric, helically coiled, tungsten wire filaments 7 and 8. The filaments 7 and 8 are connected electrically in parallel to respective lead wires 3. As here illustrated, the inner filament coil 8 is slipped snugly over the inner end of the lead wire 3. The outer filament coil 7 is connected to lead wire 3 through a pair of intermediate slip-over coils 9 and 10. The first intermediate coil 9 is in tight frictional engagement with the lead wire 3. The second intermediate coil 10 is screwed over the first coil 9, and the end of the outer filament coil 7 is screwed over the coil 10.

The fialment supports 6 are preferably tantalum discs of the type disclosed and claimed in Patent 2,813,993- Fridrich, and extending transversely between adjacent turns of filament coil 7. Each disc 6 has a central aperture therein with a collar portion at the margin thereof which clamps the disc to an adjacent turn of the outer filament coil 7. The inner filament coil 8 extends through the central apertures in the discs 6. The said discs are preferably assembled with the outer filament coil 7 before insertion of the inner filament coil into the interior of coil 7.

It will be noted that the second intermediate coil 10 is extended forwardly to the tip of the inner lead wire 3. Thus, the end of the outer filament coil 7 is short-circuited so as to reduce the voltage drop and equalize the temperatures of the wires in filament coils 7 and 8 between the lead wire 3 and the first disc 6, whereby to avoid overheating of the inner filament coil 8.

By way of example, a lamp having a quartz envelope 1 of inch outside diameter may contain an outer filament coil 7 rated at 200 watts per inch of coil length, 24 volts per inch, and about 2500 K. color temperature. Such a filament coil may consist of tungsten wire of 13.22 mil diameter wound on a 100.6 mil mandrel at 41.1 turns per inch This is about as large a filament coil as is practical for use in such lamps, since its diameter is nearly half that of the nevelope 1. In accordance with the invention, the lamp output is increased to about 300 watts per inch by addition of an inner filament 8 rated at wats per inch. Such an inner filament may consist of tungsten wire of 8.2 mil diameter, wound on a 44.6 mil mandrel at 66 turns per inch.

What I claim as new and desire to secure by Letters Patent of the United States is:

A high intensity incandescent filament lamp type radiant energy device comprising an elongated hermetically sealed envelope containing a longitudinally extending coiled tungsten wire filament structure of substantially minimal \practical diameter consuming about 300 Watts per inch of length at a potential of about 24 volts per inch, said filament structure comprising an outer helical coil of tungsten Wire of about 13.22 mil Wire diameter coiled to an inner coil diameter of about 100.6 mils at about 41.1 turns per inch and consuming about 200 watts per inch of coil length, and an inner helical coil within and coextensive with said outer coil and consisting of tungsten wire of about 8.2 mil wire diameter coiled to an inner diameter of about 44.6 mils at about 66 turns per inch and consuming about 100 watts per inch of coil length, said outer and inner coils connected in electrically parallel relationship.

References Cited by the Examiner UNITED STATES PATENTS 1,640,829 8/1927 Heany 3l33 16 X 5 2,007,923 7/1935 Braselton 313272 X 2,813,993 11/1957 Fridrich 313274 X FOREIGN PATENTS 836,407 4/ 1952 Germany.

DAVID J. GALVIN, Primary Examiner.

JAMES D. KALLAM, Examiner. 

